PureBasic Forums - English

Posted: **Wed Oct 06, 2004 12:26 am**

Is there such a thing in Purebasic as a string builder? Or some way to concatenate a lot of strings together? I know VB and C++ have some string builder classes that make appending strings very fast - is there a PB equivalent?

Posted: **Wed Oct 06, 2004 3:10 am**

Not sure is this is what you mean:

Code: Select all

w.s="ABC"
x.s="XYZ"
y.s="NOP"

z.s=w+" : "+x+" concat using plus sign "+y
Debug z

Using the + (plus) sign. If off track here, my apologies.

Posted: **Wed Oct 06, 2004 4:24 am**

No, no. Of course I know that one. I'm talking about fast string concatenation. For example, in VB, you could add strings together with the "&" symbol just fine but with several hundred additions it was slow. String builder classes could append the strings together very quickly for you. You'd create a new instance of the string builder class and usually calls sHold.Append and then when you were done, sHold.ToString (VB6).

Does this make any sense?

Posted: **Wed Oct 06, 2004 5:46 am**

Oops. Sorry Xombie.

Yes it makes sense. I am unaware of anything like this for PB.

Maybe someone else?

Posted: **Wed Oct 06, 2004 5:54 am**

is the speed of string concatenation (x.s + y.s) in PureBasic even an issue? I haven't compared this to other languages anyone else?

Posted: **Wed Oct 06, 2004 6:39 am**

Dare2 wrote:Oops. Sorry Xombie. Yes it makes sense. I am unaware of anything like this for PB.

Hello all,

First VB: It only makes sense to use string builder classes in VB, when you have to concatenate a lot of strings. Because if you do this in VB it always reallocates the string memory. I once wrote an stringbuilder class for VBScript ... it just adds the string parts to a string array (the array is not redimensioned with every new string, but in steps of 50/100 ...) ... and if you need the whole string the join() command is used to concatenate all strings. This is much ... much ... much faster than adding all string parts to one big string. If you only have to concatenate some few strings, than it makes no sense to use a string builder class.

PureBasic: I do not know how fast the realocation of strings is in PureBasic. Maybe someone can test if it would make sense to write some special concatenation functions.

cu, helpy

Posted: **Wed Oct 06, 2004 6:48 am**

Hi helpy

Further on this (hopefully this is still on topic) has anyone successfully used StrCat and similar calls, either via PB: StrCat_( or through the dll:

Code: Select all

#_shlwapi = 11
If OpenLibrary(#_shlwapi,"shlwapi.dll")
  Debug "---"
  Debug IsFunction(#_shlwapi, "StrCat") ; says no ?
  Debug IsFunction(#_shlwapi, "StrCatA") ; says no ?
  Debug IsFunction(#_shlwapi, "StrCatW") ; says YES !
  Debug IsFunction(#_shlwapi, "StringCbCat") ; says no ?
  Debug IsFunction(#_shlwapi, "StringCbCatEx") ; says no ?
; push it a bit  :)
  Debug IsFunction(#_shlwapi, "StringCbCatA") ; says no ?
  Debug IsFunction(#_shlwapi, "StringCbCatW") ; says no ?
  Debug IsFunction(#_shlwapi, "StringCbCatAEx") ; says no ?
  Debug IsFunction(#_shlwapi, "StringCbCatWEx") ; says no ?
  Debug IsFunction(#_shlwapi, "StringCbCatExA") ; says no ?
  Debug IsFunction(#_shlwapi, "StringCbCatExW") ; says no ?
  Debug "---"
  CloseLibrary(#_shlwapi)
EndIf

?

When string handling becomes bulky, important (or possibly leaky) I now use memory.

Edit:

Forgot to post what I started out to post

Helpy's post reminded me of this, by Wilbert. Maybe useful?

viewtopic.php?t=12572&highlight=

Posted: **Wed Oct 06, 2004 8:31 am**

Hi all,

I tested it with own StringBuilder functions:

Code: Select all

; Speed test of string concatenation 
; and the use of StringBuilder functions
Structure StringBuilder
  pString.l
  StringSize.l
  MemSize.l
  BlockSize.l
  InitDone.l
EndStructure

Procedure StringBuilder_Info()
  Static sbInfo.StringBuilder
  ProcedureReturn @sbInfo
EndProcedure

Procedure StringBuilder_Init(BlockSize)
  Protected *sbInfo.StringBuilder
  *sbInfo = StringBuilder_Info()
  If *sbInfo\InitDone : FreeMemory(*sbInfo\pString) : EndIf
  ; BlockSize min. 1024 ($400) Byte
  If BlockSize < $400 : BlockSize = $400 : EndIf
  ; BlockSize max. 1 MByte ($100000) Byte
  If BlockSize > $100000 : BlockSize = $100000 : EndIf
  If BlockSize <> (BlockSize & $FC00):
    BlockSize = (BlockSize & $FC00) + 1024
  EndIf
  *sbInfo\BlockSize = BlockSize
  *sbInfo\StringSize = 0
  *sbInfo\pString = AllocateMemory(BlockSize)
  If *sbInfo\pString <> 0
    *sbInfo\InitDone = #True
    *sbInfo\MemSize = *sbInfo\BlockSize
  Else
    *sbInfo\InitDone = #False
    *sbInfo\MemSize = 0
  EndIf
  ProcedureReturn *sbInfo\InitDone
EndProcedure
Procedure StringBuilder_Clear()
  Protected *sbInfo.StringBuilder
  *sbInfo=StringBuilder_Info()
  If *sbInfo\InitDone
    FreeMemory(*sbInfo\pString)
    *sbInfo\pString = 0
    *sbInfo\StringSize = 0
    *sbInfo\BlockSize = 0
    *sbInfo\InitDone = #False
    *sbInfo\MemSize = 0
  EndIf
EndProcedure
Procedure StringBuilder_Add(pAddString.l)
  Protected *sbInfo.StringBuilder
  Protected StrLen
  Protected pNewString, NewMemSize, NewStringSize
  *sbInfo = StringBuilder_Info()
  StrLen = MemoryStringLength(pAddString)
  NewStringSize = StrLen + *sbInfo\StringSize
  
  If NewStringSize + 1 > *sbInfo\MemSize
    NewMemSize = *sbInfo\MemSize+*sbInfo\BlockSize
    pNewString=AllocateMemory(NewMemSize)
    If pNewString = 0 : ProcedureReturn #False : EndIf
    CopyMemory(*sbInfo\pString,pNewString,*sbInfo\StringSize)
    FreeMemory(*sbInfo\pString)
    *sbInfo\pString=pNewString
    *sbInfo\MemSize=NewMemSize
  EndIf
  CopyMemory(pAddString,*sbInfo\pString+*sbInfo\StringSize,StrLen)
  *sbInfo\StringSize = NewStringSize
EndProcedure
Procedure.s StringBuilder_GetString()
  Protected *sbInfo.StringBuilder
  Protected WholeString.s
  *sbInfo=StringBuilder_Info()
  WholeString = PeekS(*sbInfo\pString)
  ProcedureReturn WholeString
EndProcedure

#TestLoop=1024*64

t=GetTickCount_()
For i = 1 To #TestLoop
  s1.s+"+"
Next
time1=GetTickCount_()-t
MessageRequester("StringTest", "StringFunctions: " + Str(time1) + " ms")

t=GetTickCount_()
If StringBuilder_Init(2048)
  sAdd.s="+"
  For i = 1 To #TestLoop
    StringBuilder_Add(@sAdd)
  Next
  s2.s = StringBuilder_GetString()
  StringBuilder_Clear()
  time2=GetTickCount_()-t
  MessageRequester("StringTest", "StringFunctions: " + Str(time1) + " ms" + #CRLF$ + "StringBuilder: " + Str(time2) + " ms")
  
  If CompareMemoryString(s1,s2,0) <> 0
    MessageRequester("StringTest", "Strings sind nicht identisch!")
  Else
    MessageRequester("StringTest", "Strings sind identisch!") 
  EndIf
Else
  MessageRequester("StringTest", "StringBuilder konnte nicht initialisiert werden!")
EndIf

Test: 64.000 times the character "+" is added to a string. with normal PB-String functions it takes about 11s at my PC. With the StringBuilder functions it takes 16ms.

So if you have to concatenate much strings, it makes sense to use own concatenation functions:

ATTENTION: The above functions are written only for testing. It is not possible to handel two or more strings at the same time, because there is only ONE string buffer. It would be possible to rewrite the functions to use more stringbuffers. AND the above functions does not handel the string limitations of PureBasic ... so the StringBuilder_GetString() could fail if the concatenated string is too big (at the moment a PB-String can have a maximum of 70508 characters ... tested with PB 3.91).

cu, helpy

Posted: **Wed Oct 06, 2004 9:06 am**

You can use a combination of AllocateMemory() and CopyMemoryString() which should be the fastest way to concatenate a lot of strings. See the help for CopyMemoryString() for a quick example.

Posted: **Sat Oct 09, 2004 1:02 am**

helpy - that code works great. Thanks a lot for sharing. I do wish it could be used (easily) more than once at a time but I can always adapt it as I need it.

Thanks again.

Posted: **Sun Oct 09, 2016 5:52 am**

Fred wrote:You can use a combination of AllocateMemory() and CopyMemoryString() which should be the fastest way to concatenate a lot of strings. See the help for CopyMemoryString() for a quick example.

I've been trying to do this (for fast string building, concatenation or joining) but I can't work it out.

Here's what I want to achieve:

Code: Select all

one$="111"
two$="222"

m=AllocateMemory(Len(one$)+Len(two$))
CopyMemoryString(@two$,@m)

Debug one$ ; Should output 111222

Posted: **Sun Oct 09, 2016 7:25 am**

Just a couple things to keep in mind, Len won't do for calculating memory required, StringBytelength is needed. In PB 5.50, Len is returning 3 for one$, where we know 6 bytes are needed. Also, you can't use the actual address as destination because CopyMemoryString is going to update the pointer each time it writes, adding to it the number of bytes it just wrote. So you need to set a new var to the value of your destination pointer and pass the new one to the command. Also note that after the first write no more address is needed as the command now knows where to write:

Code: Select all

one$="111"
two$="222"

*m=AllocateMemory(StringByteLength(one$)+StringByteLength(two$)+SizeOf(Character))
*writeloc = *m

CopyMemoryString(one$, @*writeloc)
CopyMemoryString(two$)

Debug PeekS(*m) ; Should output 111222

Quite a cleverly conceived command, actually. Both lightning fast and simple to code once you grasp the concept.

Posted: **Sun Oct 09, 2016 11:51 am**

Thanks netmaestro!

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